This invention relates to a display device comprising a plurality of pixels arranged in rows and columns at the location of crossings of row electrodes and column electrodes, each pixel comprising at least one field emitter connected to a cathode terminal in an electrically conducting manner and a grid electrode.
A display device of this type is usually in the form of a flat display device and is suitable, for example, for displaying video information and alpha-numerical information. A display device of this type is described in U.S. Pat. No. 5,075,591. The device shown in this document comprises strip-shaped row electrodes and column electrodes on a substrate and a matrix of pixels, each defined by a plurality of tip-shaped (pointed) field emitters on the row electrodes at the location of crossings with column electrodes. The column electrodes, which also function as grid electrodes in this case, are separated from the row electrodes by means of a layer of insulating material. At the location of the pixels, apertures are present in the column electrodes and the subjacent insulating material. Electrons released by field emission can thus be accelerated to phosphors on a faceplate located opposite the substrate.
The display device is driven by selecting a row electrode during a row selection period (which is for example 32 .mu.sec), for example, by presenting a sufficiently low voltage. Simultaneously, data voltages are presented to the column electrodes. The potential difference between the field emitters connected to the row electrodes and the grid (column) electrodes determines the emission of the associated field emitters and hence the light intensity of a pixel.
To obtain a light intensity which is as uniform as possible across the entire surface in such a display device, it is important that the field emitters behave as uniformly as possible, for example, with regard to their current-voltage characteristic. This requires a substantially identical shape of all tip-shaped (pointed) field emitters, which imposes very strict requirements from a technological point of view. Since this requirement cannot generally be satisfied in practice, an extra resistor is often arranged in series with the pixel, for example, between the field emitters and the row electrode for the purpose of uniformity. However, this leads to a higher power consumption and higher drive voltages. For these higher drive voltages it may be necessary to have drive electronics with special circuits, which may additionally increase the cost of these drive electronics, for example, because low-cost technologies such as, CMOS are no longer useable.
Moreover, it is necessary for a satisfactory operation that the column electrodes are not too far remote from the field emitters, hence from the row electrodes. However, this increases the capacitance associated with such a field emitter and hence the RC time for a presented addressing signal; as a result, the value of the signal, viewed across the length of a selection electrode, may decrease, which also gives rise to a non-uniform emission behaviour.